Solar collector module

ABSTRACT

An extended width parabolic trough solar collector (12) is supported from pylons (14). Collector (12) is formed from a center module (30) and two wing modules (32) joined together along abutting edges by connecting means. A stressed skin monocoque construction is used for each of the modules.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of application Ser. No. 06/086,314, filedon Oct. 19, 1979, of Joseph A. Hutchison now U.S. Pat. No. 4,297,003.

FIELD OF THE INVENTION

The present invention pertains to reflective trough type solarcollectors and more particularly to an extended width efficient solarcollector constructed using a plurality of high structural integritymodules connected together and the method of installing the same.

BACKGROUND ART

Systems are used to convert solar energy into other forms of energywhich can be used or stored. These systems utilize a solar collectorwhich collects the solar radiation and converts the solar energy thereininto a useable form of energy such as heat. Solar collectors of the flatplate type have been utilized in low energy applications such as heatingwater, generating low pressure steam, and supplementing air conditioningand heating systems and the like. Flat plate collectors do not focus thesun's radiation and have limited applicability. Another type ofcollector is generically called a concentrating collector. Thesecollectors function to collect the sun's radiation energy and focus orconcentrate the energy in a particular area. These concentratingcollectors can be designed to operate at high temperatures withreasonable flow rates, thus substantially increasing the versatility ofsystems incorporating these collectors over that of flat platecollectors.

One type of concentrating collector is known as the parabolic troughcollector. This type collector uses an elongated reflective troughhaving a parabolic cross-section to concentrate the sun's radiationalong a focal line extending through the focal points of the parabolicelements of the trough. A conduit can be positioned along this focalline and a heat transfer liquid can be circulated through the conduit.The liquid will be heated by the sun's energy. Satisfactory flow ratesat high temperatures can be obtained from these collectors. It has alsobeen found that by use of tracking systems these parabolic troughcollectors can become extremely efficient as they follow the movement ofthe sun. Designs for these collectors can be found in the prior art suchas is disclosed in my prior application Ser. No. 853,213 filed Nov. 21,1977, now U.S. Pat. No. 4,240,406.

Trough type collectors are becoming accepted as the most efficient andversatile means of generating energy from solar radiation. As solarsystems are used to satisfy larger energy requirements, the systemsincorporating the collectors become physically larger. Presently,systems using a plurality of collectors whose aggregate collectorsurface approaches a thousand square meters are in use. These systemshave been used as solar collectors in systems for irrigation pumping;solar heating and air conditioning; steam generation for raw crude oilprocessing and other industrial applications; generating electricalenergy directly from photovoltaic cells; and powering small powerplants.

Conventionally, trough type solar collectors have been supported on anaxis extending parallel to the focus line. These collectors arejournaled by bearings to rotate to point the reflector surface directlytoward the sun. Typically, two pylons or supports are rigidly mounted tosupport the individual collectors in a rotatable position elevated fromthe surface of the ground.

To achieve the collector areas required for some applications it hasbeen conventional to utilize collectors of a size approximately sixmeters long and approximately two and one-half meters wide. A pluralityof these collectors are mounted in an array or field. In someapplications as many as six collectors are mounted on a common axis andare mechanically connected together so that all six collectors may berotated to track the sun as a single unit. A plurality of these rows areutilized to obtain the total collector area required for the particularapplication. Attempts have been made to lower the per unit area cost ofsupport equipment such as the tracking units for each row by increasingthe length of each row. The benefit of these attempts have been offsetby the torsional flexibility added to the system by increasing theoverall length of an interconnected row of collectors and thusincreasing the length to width ratio. This flexibility creates problemsin focusing the collectors and in preventing damage to the system duringhigh winds. Stiffening the individual collector units themselves suffersfrom the disadvantage of substantially increasing the manufacturingcosts. It was also believed in the industry that attempts to increasethe width of the collector substantially beyond the two and one-halfmeter range could not be achieved due to manufacturing, structural,transportation and handling problems caused by a unit of such a size.Thus, the solar industry is faced with a problem of providing aninexpensive and efficient solar collector to satisfy large energyapplications.

One attempt to solve this problem is proposed by a Mr. Caplan in hisU.S. Pat. No. 3,959,056. To attack the problem, Mr. Caplan proposes inhis patent to use a honeycomb construction for a concentrating typecollector. Mr. Caplan suggests the provision of fabricating apparatusmounted on semitrailer trucks. The trucks are positioned at the site toproduce collectors having a width in the area of sixteen feet and alength in the area of forty feet. It is inherent in Mr. Caplan's systemthat the efficiency of a permanent factory and personnel would beabandoned and that an expensive honeycomb material construction would benecessary. The system proposed by Mr. Caplan apparently is as a resultof the inventor's (and solar industries') belief that large widthfocusing solar collectors can not be manufactured at a fixed plantbecause of the problems attendant to manufacturing, shipping, andinstallation of these large modules.

Even though this great need for collectors of substantial width isrecognized in the industry, no one to Applicant's knowledge has proposedan economical system for manufacturing and installing solar collectorsof extended width.

DISCLOSURE OF THE INVENTION

According to the present invention, a solar collector structure ofextended width is disclosed which can be constructed in an efficientmanner and which can be simply and easily transported and installed. Inaddition, a method for installing these extended width collectors isdisclosed.

More particularly, the present invention discloses a parabolic troughcollector which is constructed in modular form and which, in thepreferred embodiment, is constructed from three separate modulesextending the length of the collector. In the preferred embodiment, acenter module is provided with two wing modules connected to the edgesof the center module to form a parabolic trough. The internal surfacesof the individual modules are matched to interrelate to form a singleparabolic reflector when connected together. Accordingly, I havediscovered that I could improve my stressed-skin monocoque solarcollector construction concept which is described in my co-pendingpatent application Ser. No. 853,213 filed Nov. 21, 1977, now U.S. Pat.No. 4,240,406 to efficiently design and manufacture solar collectors ofextended width. I have accomplished this by manufacturing a plurality ofindividual modules of a monocoque stressed-skin construction of a sizewhich can be easily transported and later connecting these modulestogether to form solar collectors of extended widths. In addition, Ihave discovered that by utilizing collector modules each of whichextends the length of the collector and by connecting the edges of themodules together that an acceptable collector can be manufactured.

In one embodiment the adjoining edge of each module has a channel formedtherein and a piece of tubing is inserted into the channels and joinedthereto by suitable fasteners to interconnect the modules along theiredge. In another embodiment, a specially formed connector is fastened inplace along the edge of one of the modules and is shaped to have aprotruding portion extending along the length thereof for insertion intothe opening in a channel member connected to the adjacent module alongits edge. In still a further embodiment, an outwardly extending flangeis positioned substantially around the top and bottom surfaces of thecollector module to facilitate construction thereof.

In addition, the particular construction of the improved modularextended width solar collector is such that it lends itself well to anefficient method for installing the same. This method utilizes the stepsof first erecting spaced supporting pylons about which the collectormodule will be supported and rotate for tracking the sun's movement. Acentral module is lifted into place and supported from the two pylons atthe site. The wing modules are then coupled to the central module afterit is already in place on the pylons with the pylons acting both as asupport and as a fixture for allowing assembly of the modular collectoritself.

All of the attendant advantages and features of the present inventioncan be appreciated by referring to the details of the present inventionas shown in the accompanying drawings and as described in the detaileddescription herein.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention and theadvantages thereof, reference is now made to the following descriptiontaken in conjunction with the accompanying drawings in which:

FIG. 1 is a perspective view of one embodiment of the extended widthmodular collector of the present invention shown in a parabolic troughembodiment;

FIG. 2 is an enlarged exploded perspective view of a solar collectorformed from three modules showing two wing modules and a center moduledisconnected and with the torque transfer arms removed;

FIG. 3 is an exploded perspective view of the center module of thecollector shown in FIGS. 1 and 2;

FIG. 4 is an exploded perspective view of the wing module of thecollector shown in FIGS. 1 and 2;

FIG. 5 is a section view taken on line 5--5 of FIG. 2 looking in thedirection of the arrows showing the torque arm connected to the centermodule;

FIG. 6 is a section view taken on line 6--6 of FIG. 1 looking in thedirection of the arrows showing the preferred embodiment of theconnection between the wing and center module along one edge;

FIG. 7 is a view similar to FIG. 6 showing an alternate embodiment;

FIG. 8 is an exploded detail view showing a portion of the edge of acollector module;

FIGS. 9 and 10 are perspective views showing the method of installingthe collector of the present invention; and

FIG. 11 is a view similar to FIG. 1 showing the use of two modularcollectors connected end to end to form an increased length collectorassembly.

DETAILED DESCRIPTION OF THE INVENTION

By referring to the drawings, the details and advantages of the presentinvention will be described. Reference numerals will be used during thedescription to indicate parts or portions of the improved collectormodule of the present invention. Throughout these views, like referencecharacters will be used to designate like and corresponding parts invarious views.

In FIG. 1, the improved solar collector assembly of the presentinvention is illustrated and is identified generally by referencenumeral 10. In the embodiment illustrated, the collector assembly is ofthe parabolic trough type but it is to be understood, of course, thatother reflector shapes could be utilized to practice the presentinvention.

The collector assembly 10 is illustrated as comprising a collector 12supported from a pair of spaced vertically extending pylons 14. Thecollector 12 is shown supported from the pylons in an elevated position.The collector is mounted to rotate about a horizontally extending axis16 on shafts (not shown) which are supported in corresponding bearingsmounted on pylons 14. The pylons 14 are positioned to maximize theefficiency of the collector assembly 10 for the particular geographiclocation. In some geographical areas it may be desirable to place theaxis of rotation 16 parallel to an east-west line. In others, it may bemore efficient to place the axis of rotation 16 parallel to anorth-south line, or even some other directional bearing.

Rotation of the collector 12 about horizontal axis 16 is accomplishedthrough a suitable tracking means (not shown) which aims the collectortoward the sun to obtain maximum efficiency of the system at all times.In addition, rotation of the collector to a downwardly facing positionat night or during severe weather can be accomplished to protect thecollector from damage. A means of accomplishing mounting of thecollector and tracking is disclosed in my copending patent applicationSer. No. 864,089 filed Dec. 23, 1977 now U.S. Pat. No. 4,178,913.

The collector 12 is illustrated in FIG. 1 as a single element. It is tobe understood, of course, that a plurality of collectors 12 could beconnected in a row to allow the use of a common tracking mechanism.

The collector illustrated in FIG. 1 is an extended width collectorapproximately 6.7 meters wide. The width of the collector is shown asdimension X in FIG. 1 and represents the maximum aperture width of thecollector surface. The length of the collector is shown as dimension Y,which extends parallel to the axis of rotation 16. In the embodimentshown, the length or dimension Y is approximately 6.1 meters long.

The collector 12 has a parabolic reflective (or front) surface 18 whichextends the length of the collector. This reflective surface 18 isdesigned to focus along a focal line 20. In the embodiment shown, aconduit 22 is positioned along the focal line 20. In operation, liquidis circulated by pumps or other means not shown through the conduit 22wherein the liquid is heated by radiation energy reflected from theparabolic surface 18 and focused on the conduit 22. Energy in the formof heat can then be recovered from this fluid. In other embodiments,photovoltaic cells are placed on the collector 12 along the focal lineand are used to directly convert the solar radiation into electricalenergy.

According to a particular feature of the present invention, thecollector 12 is constructed from separate modules which are connectedtogether. Each of these modules extends the full length of a collectorand is manufactured at a plant and transported to a site and connectedtogether. In the embodiment shown, collector 12 consists of a centermodule 30 and two wing modules 32. As will be described in detail, eachof these modules is of a monocoque-stressed skin construction, i.e., theskin or covering absorbs or carries all or a large part of the stressesto which the module is exposed.

In FIG. 2, the collector 12 is illustrated in an exploded view with thewing modules 32 disconnected from the center module 30. It has beenfound that by designing each of these modules with a maximum width ofless than about two and one-half meters, the modules 30 and 32 can beeasily transported and handled by conventional means. Preferably, thecenter module 30 is symmetrical and thus both the right and left handwing modules 32 are identical in construction. As is describedhereinafter in more detail, the wing modules 32 are connected to thecenter module 30 along the edges thereof to form a rigid collectorstructure. The front surfaces 34 and 36 of the modules 30 and 32respectively are provided with a reflective coating. This coating can bea highly polished material which will reflect solar radiation. The frontreflective surfaces 34 and 36 are designed to be complementary and whenassembled together, the surfaces 34 and 36 conform to the shape of asingle parabolic trough. It is to be understood, of couse, that thereflective shape could conform to other configurations as desired by theparticular application. In the present embodiment, the shape is aparabolic trough and interior surfaces 34 and 36 are positioned toreflect the sun's radiation toward the focal line 20. Focal line 20extends parallel to the axis of rotation 16 and is occupied by theconduit 22.

In addition, a torque transfer arm assembly 40 is connected to the endsof the modules 30 and 32. Assembly 40 functions to support the collector12 from the pylons 14, to transfer torque between adjacent collectors12, and to interconnect and stiffen the modules 30 and 32. The torquetransfer arm assembly 40 has a torque transfer plate 42 which is rigidlyconnected to a shaft 44. In the present embodiment, the shaft 44 isshown welded to plate 42 but it is to be understood, of course, thatother means of attachment could be used. Plate 42 has a plurality ofbores 46 which provide clearance for fasteners 48 to extend through theplate 42 and engage portions of the modules 30 and 32 to rigidly connectthe torque transfer arm assembly 40 thereto. The shaft 44 is of a sizeand shape to be received in a conventional bearing assembly (not shown)on the pylon 14 to support the module for rotation about axis 16. Theshaft 44 can have gears or other means attached thereto to drive theshaft and thereby utilize the collector 12 for tracking movement of thesun. In addition, the shaft 44 can be of a sufficient length tointerconnect adjacent collectors 12 of a row through the spaced pylons14.

According to a particular feature of the present invention, the modules30 and 32 are of a unique monocoque stressed-skin construction. Thisconstruction is illustrated in FIGS. 3 and 4 for modules 30 and 32respectively. Modules 30 and 32 are preferably in a parabolic troughshape and utilize a plurality of precision formed bulkheads with aconcave front surface formed at close tolerances to conform to aparabolic shape. In the embodiment shown, two bulkheads or end skins areused but it is to be understood, of course, that more bulkheads could beprovided as desired. The monocoque construction of the present inventionprovides for the use of stressed skins which are rigidly fixed together.By constructing the modules 30 and 32 in this manner, stresses exertedon the structure are transferred through the stressed skins and areuniformly distributed without concentration across the entire panelstructure. This monocoque construction technique can be utilized to formmodules of sufficient strength at an economical cost.

The details of the monocoque-stressed skin construction of the module 30are illustrated in FIG. 3, wherein the module is shown in exploded form.In the embodiment shown, the module 30 has a pair of end skins orbulkheads 50 which are made from a suitable material. One method offorming these end skins or bulkheads is to cast the bulkhead and thenutilize a machining process to achieve a true parabolic shape on thefront surface of the bulkhead 50. It is desirable, of course, that thefront surface of bulkheads 50 each have a common profile so that all thebulkheads in a particular module will be substantially the same shape.It is also envisioned that the bulkheads 50 could be manufactured byroll forming the bulkhead 50 from a single sheet of material. This canbe accomplished by rolling the bulkhead with a central web portion 52and flanges 54, 56 and 58 on the front, rear and end surfacesrespectively of the bulkhead. These flanges can be rolled into positionand welded at the corners where the individual flanges come intocontact. It is also envisioned that other metal forming techniques suchas stamping or the like could be utilized, it only being important thatthe process produce a bulkhead 50 which is sufficiently rigid, hasflanges 54, 56 and 58, and has a front flange 54 which conforms to thedesired reflector shape. As will be described hereinafter in moredetail, the flanges are utilized to attach the upper and lower skins ofthe module together.

According to the embodiment of the present invention shown in FIG. 3, apair of channel members 60 are provided along the side edges of themodule 30 to form the edge skins of the module. These channel members 60are positioned so that the concave portions of the channels are facingoutward and are of a size and shape to conform to the cross-sectionalthickness of the module 30 at the edge thereof. These channels 60 arerigidly fixed to the end flanges 58 of the end bulkheads 50 by welding,or some other suitable fastening. By assembling the bulkheads 50 andchannels 60 in the quadrilateral configuration shown, furtherfabrication of the module can be performed from outside of thequadrilateral. This quadrilateral forms the edge and end skins for thestressed skin module 30.

Once this quadrilateral of the center module 30 is assembled, the frontand rear skins 62 and 64 can be attached. As previously discussed, theupper surface of the skin 62 is reflective. The skin 62 is attachedalong the edges to the quadrilateral formed by bulkheads 50 and channelmembers 60. In a similar manner, the skin 64 is attached on theunderside of the module. According to one particular advantage of thepresent invention, bulkheads 50 and channel members 60 have frontflanges which lie in a parabolic surface and contact the front skin 62.Since these flanges lie in the proper plane and extend outward from thestructure, rigid attachment of skin 62 to the frame is greatlysimplified. For example, a spot welding technique can be utilized toconnect the skin to the flanges or fasteners of conventional type can beutilized. The skin thickness should be selected to be of sufficientmagnitude to provide a monocoque construction that will operate withinthe design environment required for the module 30. Thus, the module 30when assembled has front and rear skins 62 and 64, respectively, and endedge skins formed by bulkheads 50 and channels 60, respectively. Thismonocoque construction greatly simplifies the construction of the moduleand reduces the cost thereof.

In a similar manner, the module 32 is constructed with a monocoquestressed skin construction. The details of this module 32 are shown inFIG. 4. The module 32 has a pair of end skins or bulkheads 70. Thesebulkheads 70 can be formed in the manner described with respect tobulkheads 50. Each end bulkhead 70 has front, rear and end flanges forattachment to the skins and edge channel members. The end bulkheads 70taper in thickness and the front surfaces conform to the reflectivesurface desired, such that the module 32 will mate with the module 30with the front surfaces, cooperating to form a parabolic surface.Interior skin channel 72 and exterior skin channel 74 are connected tothe bulkheads 70 are previously described with respect to module 30 toform a quadrilateral for the wing module 32. Interior channel 72 is ofthe size and shape to correspond to the size and shape of channel 60.Front skin 76 and rear skin 78 are attached to the quadrilateral aspreviously described with respect to module 30.

In FIG. 8, a typical means of fastening the skin to the flange of abulkhead or channel member is shown. In this view, the edge connectionbetween the front skin 76 and the exterior channel 74 is shown. The skin76 is welded at 80 to the outwardly extending flange of channel 74.Spaced spot welds 80 can be utilized. It is to be understood, of course,that other types of fasteners could be used.

A U-shaped clip 82 can be attached to fit over the exposed edges of theskin 76 and the flange of channel member 74. A suitable potting orsealing compound can be placed inside of the U-shaped clip 82 such thatwhen the clip is in place the exposed edges are sealed. Preferably theclip 82 is formed in a shape to resiliently grip the extending edges ofthe skin 76 and channel member 74.

The details of connection of the torque transfer arm assembly 40 areshown in FIGS. 2 through 5. As can be seen in FIGS. 2, 3 and 5, the endbulkhead 50 of the module 30 has an opening 90 aligned with axis 60 andof a size to allow insertion of shaft 44 therethrough. A shaft receivingplate assembly 92 is positioned over the opening 90. As is shown indetail in FIG. 5, the shaft receiving plate assembly 92 has acylindrical boss 94 extending out from the plate 92. The boss 94 definesa cylindrical passageway which is in alignment with opening 90, thepassageway is of a size to closely receive shaft 44 therein. A pair ofthreaded bosses 96 are spaced on either side of the boss 94 and alignwith a pair of openings 96 in the torque transfer plate 92. Suitablefasteners 48 are used to attach torque transfer plate 42 by threadedlyengaging bosses 96. Plates 100 with single threaded bosses 96 thereonare attached to the end bulkheads 50. The threaded bosses 96 are alignedwith bores 46 for receiving fasteners 48. A plate 102 is attached toeach of the bulkheads 70 adjacent to the channel 72. These plates 102have threaded bosses which align with a bore 46 in plate 42 forreceiving the fastener 48. Thus, the plate 42 rigidly connects themodules 30 and 32 together by means of the plates 92, 100 and 102 withthe shaft 44 being received within the boss 94.

According to another feature of the present invention, modules 30 and 32are each connected together along abutting edges. The details of thisconnection are illustrated in FIG. 6, wherein a typical connection canbe seen. The concave portions of the edge of channels 60 and 72 formelongated sockets extending the length of the modules. When the modules30 and 32 are placed with their edges abutting, a chamber 110 is formedby the sockets in channels 60 and 72. In the embodiment illustrated,tubing 112 has a cross-sectional size and shape to fit in the chamber110. In the embodiment shown the tubing is rectangular. Suitable boresare formed in the modules 30 and 32 for receiving fasteners 114therethrough. As seen in FIG. 6, a fastener 114 extends through themodule 32 and tubing 112 to connect the module 32 to the tubing 112. Ina similar manner, a fastener 114 extends through the module 30 andthrough the square tubing 112 to rigidly interconnect the module 30 and32. The bores for fasteners 114 can be pre-drilled and pre-aligned atthe site of manufacture of the modules and can be inserted at theinstallation site, allowing transportation of the modules in theunassembled form.

An alternate embodiment for connecting the modules is shown in FIG. 7.In this embodiment, the module 30 has a channel member 60 as previouslydescribed. The module 32', however, is different in construction fromthe module 32 and in place of channel 72 a special roll formed closedtubing section 120 is affixed. This section 120 has a portion of aproper width to contact skins 76 and 78. A reduced thickness protrudingportion 122 is provided of a size to fit inside the channel member 60and receive a fastener 114 through suitable clearance openings to attachthe modules.

It should be appreciated that the structure of the collector 12 is suchthat it lends itself simply and easily to transportation andinstallation. In FIGS. 9 and 10, the basic steps of installation areillustrated. In FIG. 9, the pylons 14 are shown installed on suitablefoundations. Thereafter the center module 30 can be lowered in place andmounted on the pylons as shown in FIG. 10. Next, a wing module 32 can belowered into place and connected along one edge of the module 30.Finally, the other wing module 32 can be connected to the other side ofthe center module 30. Subsequently the conduit 22 shown in FIG. 1 andthe tracking apparatus (not shown) can be installed.

In FIG. 11, another embodiment of the improved solar collector 12 of thepresent invention is shown. In this embodiment two collectors 12 areshown attached end to end to form a longer collector assembly 130without pylons between the individual collectors 12. This isaccomplished by using a connecting means such as is used along the edgesof the individual modules 30 and 32 of the collector structure itself.

It is to be appreciated, of course, that the present invention isillustrated and described by reference to preferred embodiments and thatnumerous alterations and modifications may be made thereof withoutdeparting from the spirit and scope of the present invention. It is alsoanticipated that the present invention could be applied to constructcollectors from more or less than three modules.

I claim:
 1. A solar collector comprising: at least two elongated moduleshaving a reflective surface on the front sides thereof wherein thereflective surfaces of said modules conform to a particular reflectiveshape; connector means comprising channel members fastened to theabutting edges of each of said modules adjacent the connection point andextending the length thereof; a connector extending into the interior ofsaid channel members and being fastened to each of said modules byfasteners.
 2. A solar collector comprising: at least two elongated solarcollector modules each having a reflective surface on the front sidethereof, said surfaces cooperating to form a curved reflective surfacethat is adapted to focus solar radiation along a single focal lineparallel to the longitudinal axes of said modules when said modules arejoined along the adjacent edges thereof, means joining said modulestogether along said adjacent edges, said joining means comprisingchannel members fastened to the adjacent edges of each of said modulesand extending the length thereof for connecting said modules; andconnector means extending into the interior of said channel members foruse in connecting said modules.
 3. A solar collector comprising: atleast two connected elongated modules each having a reflective surfaceon the front sides thereof; said surfaces cooperating to form a curvedreflective surface that is adapted to focus solar radiation along asingle focal line parallel to the longitudinal axes of said modules;channel members fastened adjacent to the edges of said modules andextending the length thereof for connecting said modules; and connectormeans extending into the interior of said channel members for connectingthe channel members of adjacent modules.